Thank you for your patience while we worked on this, a fix for this issue was just rolled out and should take effect the next time you start Studio.
Switching between Actual Resolution and Fit To Window should work as expected. There is a known issue with switching between Actual Resolution and Physical Size after switching to a new experience, a fix for that will be coming in the next few weeks as we complete testing and can get that change released.
This issue was an unintended side effect of a larger refactor that was taking place, and we weren’t able to address this specific issue until that refactor was complete.